The use of solar energy to heat fluids is an old and well-known procedure which has in recent years evoked greater interest because of the increasing shortage of fossil fuels which are most commonly used for such heating purposes.
While the basic technology of utilizing the sun's rays to heat a fluid, such as a liquid or a gas, is known, this technology has found limited application because of the difficulty in making apparatus for this purpose which is efficient and relatively inexpensive. In large measure, cost of equipment and of on-site assembly thereof have been a major problem mitigating against use of solar energy cells to heat small structures such as one-family residences.
Thus, most solar heating units must be especially fabricated for the particular structure to be heated. Therefore, such units being custom fabricated are quite expensive and their use generally limited to large commercial or educational buildings. Attempts to overcome this problem by having a standard factory manufactured solar collector for smaller structures have not been successful since such structures vary so widely in heating requirements because of their size differences, various types of construction, local climatic conditions, and the like, that there is no one collector size that is suitable for any large percentage of these structures. Modular units have, heretofore, also not been entirely practical because of the difficulty and cost of assembling and disassembling them for use.